// channel-irc — Standalone IRC channel daemon
//
// Maintains a persistent TLS connection to an IRC server, parses
// incoming messages, and serves them over the channel.capnp protocol
// on a Unix socket at ~/.consciousness/channels/irc.sock.
//
// Runs independently of the consciousness binary so restarts don't
// kill the IRC connection. Reconnects automatically with exponential
// backoff. Supports multiple simultaneous capnp clients.
//
// Config: ~/.consciousness/channels/irc.json5
// Socket: ~/.consciousness/channels/irc.sock

use std::cell::RefCell;
use std::collections::VecDeque;
use std::io;
use std::path::PathBuf;
use std::rc::Rc;
use std::sync::Arc;

use capnp::capability::Promise;
use capnp_rpc::{pry, rpc_twoparty_capnp, twoparty, RpcSystem};
use futures::AsyncReadExt;
use tokio::io::{AsyncBufReadExt, AsyncWriteExt, BufReader};
use tokio::net::UnixListener;
use tokio_util::compat::TokioAsyncReadCompatExt;
use tracing::{error, info, warn};

use poc_memory::channel_capnp::{channel_client, channel_server};

// ── Constants ──────────────────────────────────────────────────

const MAX_HISTORY: usize = 1000;
const RECONNECT_BASE_SECS: u64 = 5;
const RECONNECT_MAX_SECS: u64 = 300;
const PING_INTERVAL_SECS: u64 = 120;
const PING_TIMEOUT_SECS: u64 = 30;

// Urgency levels (matching thalamus/notify.rs)
const AMBIENT: u8 = 0;
const NORMAL: u8 = 2;
const URGENT: u8 = 3;

// ── Config ─────────────────────────────────────────────────────

#[derive(Clone, serde::Deserialize)]
struct Config {
    server: String,
    port: u16,
    #[serde(default = "default_true")]
    tls: bool,
    nick: String,
    channels: Vec<String>,
    #[serde(default)]
    password: Option<String>,
    #[serde(default)]
    nickserv_pass: Option<String>,
}

fn default_true() -> bool { true }

fn load_config() -> Config {
    let path = dirs::home_dir()
        .unwrap_or_default()
        .join(".consciousness/channels/irc.json5");
    let text = std::fs::read_to_string(&path)
        .unwrap_or_else(|e| panic!("failed to read {}: {e}", path.display()));
    json5::from_str(&text)
        .unwrap_or_else(|e| panic!("failed to parse {}: {e}", path.display()))
}

// ── IRC Message Parsing ────────────────────────────────────────

struct IrcMessage {
    prefix: Option<String>,
    command: String,
    params: Vec<String>,
}

impl IrcMessage {
    fn parse(line: &str) -> Option<Self> {
        let line = line.trim_end_matches(|c| c == '\r' || c == '\n');
        if line.is_empty() {
            return None;
        }

        let (prefix, rest) = if line.starts_with(':') {
            let space = line.find(' ')?;
            (Some(line[1..space].to_string()), &line[space + 1..])
        } else {
            (None, line)
        };

        let (command_params, trailing) = if let Some(pos) = rest.find(" :") {
            (&rest[..pos], Some(rest[pos + 2..].to_string()))
        } else {
            (rest, None)
        };

        let mut parts: Vec<String> = command_params
            .split_whitespace()
            .map(String::from)
            .collect();

        if parts.is_empty() {
            return None;
        }

        let command = parts.remove(0).to_uppercase();
        let mut params = parts;
        if let Some(t) = trailing {
            params.push(t);
        }

        Some(IrcMessage { prefix, command, params })
    }

    fn nick(&self) -> Option<&str> {
        self.prefix.as_deref().and_then(|p| p.split('!').next())
    }
}

// ── Writer Abstraction ─────────────────────────────────────────

type WriterHandle = Box<dyn AsyncWriter>;

trait AsyncWriter {
    fn write_line(
        &mut self,
        line: &str,
    ) -> std::pin::Pin<Box<dyn std::future::Future<Output = io::Result<()>> + '_>>;
}

struct TlsWriter {
    inner: tokio::io::WriteHalf<tokio_rustls::client::TlsStream<tokio::net::TcpStream>>,
}

impl AsyncWriter for TlsWriter {
    fn write_line(
        &mut self,
        line: &str,
    ) -> std::pin::Pin<Box<dyn std::future::Future<Output = io::Result<()>> + '_>> {
        let data = format!("{line}\r\n");
        Box::pin(async move { self.inner.write_all(data.as_bytes()).await })
    }
}

struct PlainWriter {
    inner: tokio::io::WriteHalf<tokio::net::TcpStream>,
}

impl AsyncWriter for PlainWriter {
    fn write_line(
        &mut self,
        line: &str,
    ) -> std::pin::Pin<Box<dyn std::future::Future<Output = io::Result<()>> + '_>> {
        let data = format!("{line}\r\n");
        Box::pin(async move { self.inner.write_all(data.as_bytes()).await })
    }
}

// ── State ──────────────────────────────────────────────────────

use poc_memory::thalamus::channel_log::ChannelLog;

struct State {
    config: Config,
    /// Per-channel message logs (keyed by channel path, e.g. "irc.#bcachefs")
    channel_logs: std::collections::BTreeMap<String, ChannelLog>,
    /// Currently joined channels
    channels: Vec<String>,
    connected: bool,
    /// IRC writer handle (None when disconnected)
    writer: Option<WriterHandle>,
    /// Registered notification callbacks
    subscribers: Vec<channel_client::Client>,
}

type SharedState = Rc<RefCell<State>>;

impl State {
    fn new(config: Config) -> Self {
        let channels = config.channels.clone();
        Self {
            config,
            channel_logs: std::collections::BTreeMap::new(),
            channels,
            connected: false,
            writer: None,
            subscribers: Vec::new(),
        }
    }

    fn push_message(&mut self, line: String, urgency: u8, channel: &str) {
        // Store in per-channel log
        self.channel_logs
            .entry(channel.to_string())
            .or_insert_with(ChannelLog::new)
            .push(line.clone());

        // Notify all subscribers
        let preview = line.chars().take(80).collect::<String>();
        for sub in &self.subscribers {
            let mut req = sub.notify_request();
            let mut list = req.get().init_notifications(1);
            let mut n = list.reborrow().get(0);
            n.set_channel(channel);
            n.set_urgency(urgency);
            n.set_preview(&preview);
            n.set_count(1);
            tokio::task::spawn_local(async move {
                let _ = req.send().promise.await;
            });
        }
    }

    async fn send_raw(&mut self, line: &str) -> io::Result<()> {
        if let Some(ref mut w) = self.writer {
            w.write_line(line).await
        } else {
            Err(io::Error::new(io::ErrorKind::NotConnected, "irc: not connected"))
        }
    }

    async fn send_privmsg(&mut self, target: &str, msg: &str) -> io::Result<()> {
        self.send_raw(&format!("PRIVMSG {target} :{msg}")).await
    }
}

// ── Persistence ────────────────────────────────────────────────

fn data_dir() -> PathBuf {
    dirs::home_dir().unwrap_or_default().join(".consciousness/irc")
}

fn append_log(target: &str, nick: &str, text: &str) {
    use std::io::Write;
    let filename = format!("{}.log", target.trim_start_matches('#').to_lowercase());
    let dir = data_dir().join("logs");
    let _ = std::fs::create_dir_all(&dir);
    if let Ok(mut f) = std::fs::OpenOptions::new()
        .create(true)
        .append(true)
        .open(dir.join(&filename))
    {
        let secs = now() as u64;
        let _ = writeln!(f, "{secs} <{nick}> {text}");
    }
}

fn now() -> f64 {
    std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .unwrap_or_default()
        .as_secs_f64()
}

// ── TLS ────────────────────────────────────────────────────────

fn root_certs() -> rustls::RootCertStore {
    let mut roots = rustls::RootCertStore::empty();
    roots.extend(webpki_roots::TLS_SERVER_ROOTS.iter().cloned());
    roots
}

// ── IRC Connection Loop ────────────────────────────────────────

async fn connection_loop(state: SharedState) {
    let _ = std::fs::create_dir_all(data_dir().join("logs"));
    let mut backoff = RECONNECT_BASE_SECS;

    loop {
        let config = state.borrow().config.clone();
        info!("irc: connecting to {}:{}", config.server, config.port);

        match connect_and_run(&state, &config).await {
            Ok(()) => info!("irc: connection closed cleanly"),
            Err(e) => error!("irc: connection error: {e}"),
        }

        let was_connected = state.borrow().connected;
        {
            let mut s = state.borrow_mut();
            s.connected = false;
            s.writer = None;
        }
        if was_connected {
            backoff = RECONNECT_BASE_SECS;
        }

        info!("irc: reconnecting in {backoff}s");
        tokio::time::sleep(std::time::Duration::from_secs(backoff)).await;
        backoff = (backoff * 2).min(RECONNECT_MAX_SECS);
    }
}

async fn connect_and_run(state: &SharedState, config: &Config) -> io::Result<()> {
    let addr = format!("{}:{}", config.server, config.port);
    let tcp = tokio::net::TcpStream::connect(&addr).await?;

    if config.tls {
        let tls_config = rustls::ClientConfig::builder_with_provider(
            rustls::crypto::ring::default_provider().into(),
        )
        .with_safe_default_protocol_versions()
        .map_err(|e| io::Error::new(io::ErrorKind::Other, e))?
        .with_root_certificates(root_certs())
        .with_no_client_auth();
        let connector = tokio_rustls::TlsConnector::from(Arc::new(tls_config));
        let server_name = rustls::pki_types::ServerName::try_from(config.server.clone())
            .map_err(|e| io::Error::new(io::ErrorKind::InvalidInput, e))?;
        let tls_stream = connector.connect(server_name, tcp).await?;

        let (reader, writer) = tokio::io::split(tls_stream);
        state.borrow_mut().writer = Some(Box::new(TlsWriter { inner: writer }));
        register_and_read(state, config, BufReader::new(reader)).await
    } else {
        let (reader, writer) = tokio::io::split(tcp);
        state.borrow_mut().writer = Some(Box::new(PlainWriter { inner: writer }));
        register_and_read(state, config, BufReader::new(reader)).await
    }
}

async fn register_and_read<R: tokio::io::AsyncRead + Unpin>(
    state: &SharedState,
    config: &Config,
    mut reader: BufReader<R>,
) -> io::Result<()> {
    // Send PASS if configured
    if let Some(ref pass) = config.password {
        state.borrow_mut().send_raw(&format!("PASS {pass}")).await?;
    }

    // Register with nick and user
    {
        let mut s = state.borrow_mut();
        s.send_raw(&format!("NICK {}", config.nick)).await?;
        s.send_raw(&format!("USER {} 0 * :{}", config.nick, config.nick)).await?;
    }

    let mut buf = Vec::new();
    let mut ping_sent = false;
    let mut deadline = tokio::time::Instant::now()
        + std::time::Duration::from_secs(PING_INTERVAL_SECS);

    loop {
        buf.clear();

        let read_result = tokio::select! {
            result = reader.read_until(b'\n', &mut buf) => result,
            _ = tokio::time::sleep_until(deadline) => {
                if ping_sent {
                    return Err(io::Error::new(
                        io::ErrorKind::TimedOut,
                        "ping timeout -- no response from server",
                    ));
                }
                info!("irc: no data for {PING_INTERVAL_SECS}s, sending PING");
                state.borrow_mut().send_raw("PING :keepalive").await?;
                ping_sent = true;
                deadline = tokio::time::Instant::now()
                    + std::time::Duration::from_secs(PING_TIMEOUT_SECS);
                continue;
            }
        };

        let n = read_result?;
        if n == 0 {
            break;
        }

        // Any data resets the ping timer
        ping_sent = false;
        deadline = tokio::time::Instant::now()
            + std::time::Duration::from_secs(PING_INTERVAL_SECS);

        // IRC is not guaranteed UTF-8
        let line = String::from_utf8_lossy(&buf).trim_end().to_string();
        if line.is_empty() {
            continue;
        }
        let msg = match IrcMessage::parse(&line) {
            Some(m) => m,
            None => continue,
        };

        match msg.command.as_str() {
            "PING" => {
                let arg = msg.params.first().map(|s| s.as_str()).unwrap_or("");
                state.borrow_mut().send_raw(&format!("PONG :{arg}")).await?;
            }

            // RPL_WELCOME -- registration complete
            "001" => {
                info!("irc: registered as {}", config.nick);
                state.borrow_mut().connected = true;

                // NickServ auth
                if let Some(ref pass) = config.nickserv_pass {
                    state.borrow_mut()
                        .send_privmsg("NickServ", &format!("IDENTIFY {pass}"))
                        .await?;
                }

                // Join configured channels
                let channels = state.borrow().channels.clone();
                for ch in &channels {
                    if let Err(e) = state.borrow_mut().send_raw(&format!("JOIN {ch}")).await {
                        warn!("irc: failed to join {ch}: {e}");
                    }
                    // Create log entry so channel appears in list()
                    let key = format!("irc.{ch}");
                    state.borrow_mut().channel_logs
                        .entry(key)
                        .or_insert_with(ChannelLog::new);
                }
            }

            "PRIVMSG" => {
                let target = msg.params.first().map(|s| s.as_str()).unwrap_or("");
                let text = msg.params.get(1).map(|s| s.as_str()).unwrap_or("");
                let nick = msg.nick().unwrap_or("unknown");

                // Handle CTCP requests
                if text.starts_with('\x01') && text.ends_with('\x01') {
                    let ctcp = &text[1..text.len() - 1];
                    if ctcp.starts_with("VERSION") {
                        let reply = format!(
                            "NOTICE {nick} :\x01VERSION poc-channel-irc 0.1.0\x01"
                        );
                        state.borrow_mut().send_raw(&reply).await.ok();
                    }
                    continue;
                }

                // Format and classify
                let (log_line, channel, urgency) = if target.starts_with('#') {
                    let line = format!("[{}] <{}> {}", target, nick, text);
                    let ch = format!("irc.{}", target);
                    let urg = if text.to_lowercase().contains(&config.nick.to_lowercase()) {
                        NORMAL // mentioned
                    } else {
                        AMBIENT
                    };
                    (line, ch, urg)
                } else {
                    // Private message
                    let line = format!("[PM:{}] {}", nick, text);
                    let ch = format!("irc.pm.{}", nick.to_lowercase());
                    (line, ch, URGENT)
                };

                // Per-channel log file
                if target.starts_with('#') {
                    append_log(target, nick, text);
                } else {
                    append_log(&format!("pm-{nick}"), nick, text);
                }

                state.borrow_mut().push_message(log_line, urgency, &channel);
            }

            "NOTICE" => {
                let text = msg.params.last().map(|s| s.as_str()).unwrap_or("");
                let from = msg.nick().unwrap_or("server");
                let log_line = format!("[notice:{}] {}", from, text);
                state.borrow_mut().push_message(log_line, AMBIENT, "irc.server");
            }

            // Nick in use
            "433" => {
                let alt = format!("{}_", config.nick);
                warn!("irc: nick in use, trying {alt}");
                state.borrow_mut().send_raw(&format!("NICK {alt}")).await?;
            }

            "JOIN" | "PART" | "QUIT" | "KICK" | "MODE" | "TOPIC" => {
                // Silent for now
            }

            _ => {}
        }
    }

    Ok(())
}

// ── ChannelServer Implementation ───────────────────────────────

struct ChannelServerImpl {
    state: SharedState,
}

impl channel_server::Server for ChannelServerImpl {
    fn recv(
        &mut self,
        params: channel_server::RecvParams,
        mut results: channel_server::RecvResults,
    ) -> Promise<(), capnp::Error> {
        let params = pry!(params.get());
        let channel = pry!(pry!(params.get_channel()).to_str()).to_string();
        let all_new = params.get_all_new();
        let min_count = params.get_min_count() as usize;

        let mut s = self.state.borrow_mut();
        let text = match s.channel_logs.get_mut(&channel) {
            Some(log) => {
                if all_new { log.recv_new(min_count) } else { log.recv_history(min_count) }
            }
            None => String::new(),
        };

        results.get().set_text(&text);
        Promise::ok(())
    }

    fn send(
        &mut self,
        params: channel_server::SendParams,
        _results: channel_server::SendResults,
    ) -> Promise<(), capnp::Error> {
        let params = pry!(params.get());
        let channel = pry!(pry!(params.get_channel()).to_str()).to_string();
        let message = pry!(pry!(params.get_message()).to_str()).to_string();

        // Parse channel path to IRC target:
        //   irc.#bcachefs  -> #bcachefs
        //   irc.pm.nick    -> nick (PRIVMSG)
        let target = channel_to_target(&channel);

        let state = self.state.clone();
        Promise::from_future(async move {
            {
                let mut s = state.borrow_mut();
                s.send_privmsg(&target, &message).await
                    .map_err(|e| capnp::Error::failed(format!("send failed: {e}")))?;
            }

            let nick = state.borrow().config.nick.clone();
            append_log(&target, &nick, &message);

            let log_line = if target.starts_with('#') {
                format!("[{}] <{}> {}", target, nick, message)
            } else {
                format!("[PM:{}] {}", target, message)
            };
            state.borrow_mut().push_message(log_line, 0, &channel);

            Ok(())
        })
    }

    fn subscribe(
        &mut self,
        params: channel_server::SubscribeParams,
        _results: channel_server::SubscribeResults,
    ) -> Promise<(), capnp::Error> {
        let callback = pry!(pry!(params.get()).get_callback());
        self.state.borrow_mut().subscribers.push(callback);
        info!("client subscribed for notifications");
        Promise::ok(())
    }

    fn list(
        &mut self,
        _params: channel_server::ListParams,
        mut results: channel_server::ListResults,
    ) -> Promise<(), capnp::Error> {
        let s = self.state.borrow();
        let connected = s.connected;

        // All channels with logs (joined + PMs)
        let names: Vec<String> = s.channel_logs.keys().cloned().collect();
        let mut list = results.get().init_channels(names.len() as u32);
        for (i, name) in names.iter().enumerate() {
            let mut entry = list.reborrow().get(i as u32);
            entry.set_name(name);
            entry.set_connected(connected);
            entry.set_unread(
                s.channel_logs.get(name).map_or(0, |l| l.unread())
            );
        }

        Promise::ok(())
    }
}

/// Convert a channel path to an IRC target.
///   "irc.#bcachefs"  -> "#bcachefs"
///   "irc.pm.nick"    -> "nick"
///   "#bcachefs"      -> "#bcachefs"  (passthrough)
fn channel_to_target(channel: &str) -> String {
    if let Some(rest) = channel.strip_prefix("irc.") {
        if let Some(nick) = rest.strip_prefix("pm.") {
            nick.to_string()
        } else {
            // rest is "#bcachefs" or similar
            rest.to_string()
        }
    } else {
        channel.to_string()
    }
}

// ── Main ───────────────────────────────────────────────────────

#[tokio::main(flavor = "current_thread")]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    tracing_subscriber::fmt::init();

    let config = load_config();
    let state = Rc::new(RefCell::new(State::new(config)));

    let sock_dir = dirs::home_dir()
        .unwrap_or_default()
        .join(".consciousness/channels");
    std::fs::create_dir_all(&sock_dir)?;
    let sock_path = sock_dir.join("irc.sock");
    let _ = std::fs::remove_file(&sock_path);

    info!("irc channel daemon starting on {}", sock_path.display());

    tokio::task::LocalSet::new()
        .run_until(async move {
            // Start IRC connection loop
            let irc_state = state.clone();
            tokio::task::spawn_local(async move {
                connection_loop(irc_state).await;
            });

            // Listen for channel protocol connections
            let listener = UnixListener::bind(&sock_path)?;

            loop {
                let (stream, _) = listener.accept().await?;
                let (reader, writer) = stream.compat().split();
                let network = twoparty::VatNetwork::new(
                    futures::io::BufReader::new(reader),
                    futures::io::BufWriter::new(writer),
                    rpc_twoparty_capnp::Side::Server,
                    Default::default(),
                );

                let server = ChannelServerImpl {
                    state: state.clone(),
                };
                let client: channel_server::Client =
                    capnp_rpc::new_client(server);

                let rpc_system = RpcSystem::new(
                    Box::new(network),
                    Some(client.client),
                );

                tokio::task::spawn_local(rpc_system);
                info!("channel client connected");
            }

            #[allow(unreachable_code)]
            Ok::<(), Box<dyn std::error::Error>>(())
        })
        .await
}